With the recent increased demand for high surface recording densities in excess of 1 TB/in2, there is an additional demand for further miniaturization of the process of writing onto a magnetic recording medium. Along with this increased demand, there is a problem of heat fluctuation with magnetization caused by the instability of magnetized regions of the medium. The perpendicular magnetic recording system is a method of resolving this difficulty which records magnetized signals in a direction perpendicular to the medium. However, even with this perpendicular magnetic recording system, miniaturization of the single magnetic pole used for writing which generates a perpendicular recording magnetic field in the medium to increase the surface recording density means that it continues to be difficult to generate a vertical magnetic field sufficient to reverse the magnetism in the recording medium.
To supplement the inadequacy of the magnetic field strength for writing, there is a method of supplying magnetic flux to the write magnetic pole by providing a subsidiary magnetic pole which increases the volume of the magnetic body in the height wise direction the floating surface, and a method of shortening the throat height (the range which determines the width of the write magnetic pole) moving the saturation point of the magnetic field closer to the floating surface and ensuring the strength of the magnetic field. However, when the throat height is shortened, the flare section which concentrates the magnetic field generated by coil induction and brings it to the floating surface is also brought closer to the floating surface. The flare section has a shape which is long horizontally and has an angle of spread greater than about 90° to prevent erasure or deterioration of data due to residual magnetic flux after writing, but there is a difficulty in that the recording width increases relative to the geometrical width of the single pole used for writing because of magnetic field leakage from the flare section due to the shape anisotropy provided to ensure the magnetic domain remains parallel to the recording medium.
If the spread angle of the flare section is kept below 90° to reduce writing bleed caused by the spread of recording width due to leakage of magnetic flux, magnetic domain control in the main magnetic pole is a key issue with the shape of the flare section relative to the floating surface becoming long in a vertical direction, the magnetic domain moving in a direction perpendicular to the recording medium with the shape anisotropy, and the danger of erasure after writing with residual flux from the recording head erasing data in the recording medium.
A means of controlling the magnetic domain of the main magnetic pole has been disclosed in respect to erasure after writing. In the gazettes of Japanese Patent Nos. 1995-21515, 2000-339621, and 1999-31306, a method is disclosed of controlling the magnetic domain by texturing the surface of the lowest layer of the recording head. Moreover, Japanese Patent No. 2004-139676 discloses a method of controlling the magnetic domain of the main magnetic pole using a film in which there is a magnetic phase transition from a non-magnetic state to a magnetic state by irradiating different wavelengths on the trailing side of the main magnetic pole.